First, you.Quit buying into his nonsense! I want you to stop thinking of yourself as pathetic, effective immediately.Yes, you do have a responsibility to learn. That is your portion of the teacher-student arrangement. But if the information is not presented to you in the first place, you don't get to do your part.

Now, him.He is a jerk.He doesn't understand the simple basics of teaching.Even if he has some unspoken problem with you, he has to hold up his end and teach.

Now, the school.The owner, chief instructor, whoever want to know about this. Chances are really good that you are not the only person on the stinky end of his teaching stick.

Now, me.As an instructor, it was my responsibility to correct student's technique all the time. Over the years, I developed a process to make it work out better.Every time I made a negative comment on a student's technique, I considered it as if it was a small cut or opened something with that person. Naturally, I would make the needed correction on the spot and then continue my cruising around the room. Eventually, I made a point of stopping back at that student to close the issue by seeing how they are progressing. Some sort of positive comment usually followed, if only to encouraage them to keep trying and commend the effort.

Of course everyone has their own teaching style, but it would never occour to me to belittle anyone, much less be a party to a student beating themself up.

Go talk to the guy. Like, what's the worst that can happen, he starts treating you badly?